Automatic radio direction finder



1954 D. w. G. BYATT ,69 ,406

AUTOMATIC RADIO DIRECTION FINDER Filed March 16, 1953 2 Sheets-Sheet l A! T! 5 7 1 IMPEDANCE Z 2 h RIF-I Z2 8.? 2 i #2 'IMPEDANCE 1 2 (MQEDANCE IMPEDANCE I Nov. 23, 1954 D. w. G. BYATT 2,695,406

AUTOMATIC RADIO DIRECTION FINDER Filed March 16, 1955 2 Sheets-Sheet 2 E CTI MPLIFIE E United States arena 2,695,406- AUTOMATIC nAi io DrRECTioN return Dennis William George h'yatt, chigiiaiiClleiiiisfford,,Eiig land, assignor to Marconis Wireless Telegraph fining pauy Limited, London, England, a company of Great Britain Ap ucaaan March 16, 1953, sienai Nd. 342,463 Claims priority, application @reat iiritain April scram-s. (Cl;34311 8)' This invention relates to automatic radm direction finders and has for its objectto' provide improved, simple, direct reading automatic radio dire ctiongfinders spitable for use on very high frequencies, which shall ,be of high efiiciency and free from the relatively high insertion losses caused by the radiog oniometers in the usual known automatic direct reading direction finders... a i 7 According to this invention a radio direction finder comprises two similar mutually perpendicular pairs of spaced aerials and a central aerial, two impedances of different Values so chosen that when on'e is fully coupled as a terminating impedance to one and the other is fully coupled as a terminating impedance to the other of two aerials of a'pairsaid one aerial-acts substantially as a director and said other acts substantially as a reflector for the central aerial, a rotary coupling device having a stator with elements coupled to the four spaced aerials and a rotor with elements coupled to the two impedances and adapted, on rotation, to couple said impedances in turn to the two pairs of spaced aerials, one to each aerial of a pair, a receiver fed from the central aerial, means driven in synchronism with said rotor for producing a reference phase signal, means for comparing said reference phase signal with the phase of the output from the receiver and a direction indicator actuated by the output from the phase comparing means.

The aerial system may consist of two mutually perpendicular pairs of vertical dipoles, the dipoles of each pair being spaced approximately at a quarter of a wave length apart, and a similar vertical central dipole, though, in a preferred arrangement unipoles are employed instead of dipoles.

Preferably the rotary coupling device is a variable capacity coupler having four stator plates arranged round a circle and each coupled to one of the four aerials of the two pairs, and two diametrically opposite rotor plates one earthed through one impedance and the other earthed through the other. The stator plates may with advantage be of sinusoidal shape and the rotor plates of part cylindrical shape.

The invention is illustrated in the accompanying drawings which show two embodiments. In the drawings, which are purely diagrammatic Figure 1 diagrammatically represents one pair of aerials, the central aerial, the capacity coupling device and the two impedances, Figure 2 is a diagrammatic plan view showing the coupling device, the two impedances and all five aerials, Figure 3 is a general diagram in which, for purposes of simplicity of drawing, the central aerial is shown outside the four aerials constituting the two pairs though actually it is centraly positioned with respect thereto, while Figure 4 shows, in manner similar to that adopted for Figure 3, a modification in which unipoles replace the dipoles of Figure 3.

Referring to Figures 1 to 3 the aerial system in the installation therein shown comprises four aerials 1, 2, 3, 4, in which 1 and 2 constitute one pair and 3 and 4 constitute the other, and a central aerial 5. All the aerials are similar dipoles mounted vertically in any convenient manner and the aerials of each pair, i. e. 1 and 2 on the one hand and 3 and 4 on the other, are approximately a quarter of a wave length apart. The two pairs are mutually perpendicular. There is a rotary capacity coupling device comprising a stator consisting of four plates S1. S2. S3 and S4 and a rotor consisting of two plates R1, R2 the stator plates lying on the circumference of 2,695,406 Patented Nov. 23, 1954 an imaginary cylinder and the rotor plates lying on represented as though they were simply loads; .As will" be seen, and as bestzshown inFig'ure 2, on rotation of the rotor the plates R1, R2 will in one position provide maximum coupling with the plates S1 and S2;.45 later they will provide equal coupling to all" four stator plates; and 45 still laterwill provide maximum coupling; to the plates S3 and S4 and so on; The stator plate R1 is earthed through: an impedance Z1 and the stator plate R2 is earthed. through an impedance Z2- These impedances are' of different magnitudes such. that, when maximum coupling is provided to' one pair of stator plates, one of the two aerials connected to those stator plates acts as a reflectorv and the other as a director for. the central aerial 5. The rotor. is driven by a motor M' onthe shaft of' which is provided any convenient form F of A. C. generator G represented purely diagrammatically in-Figure 3 and which is adapted to provide a reference phase signal of predetermined periodicity as therotor rotates" e. g: 25 c; p: s. The central aerial 5 feeds irito a receiver 6 followed by a selective amplifier 1; The

output from the generator G is fed to a selective amplifier 8 and the outputs from the two selective amplifiers are phase compared in a phase comparison circuit 9 of any kind known per se, the output from which operates a direct reading direction indicator represented schematically at 10.

With this arrangement, if it be assumed that the rotor is in the position of maximum coupling with one pair of aerials, those aerials together with the central aerial, act, in effect, as a Yagi system with directional properties. As the rotor rotates, the asymetrical polar diagram of the system also rotates the coupler acting in effect as a rotary coupling switch. When an incoming signal from a particular direction strikes the aerial system an amplitude modulation is impressed upon the signal received by the central aerial element 5 and the phase of this modulation will depend on the incoming signal direction. By suitable choice of the shape of the plates in the coupling device the phase of the modulation may be directly related to the incoming direction. In the preferred arrangement employed, the stator plates S1, S2, S3, S4 are made of sinusoidal shape and the rotor plates of part cylindrical shape (these shapes being exceedingly well known per se it is not thought necessary to show them in the drawing) so that sinusoidal modulation is impressed upon the carrier received by the aerial 5. This modulated signal, after reception by the normal receiver 6, produces a sinusoidal wave whose phase compared with an arbitrary datum is directly related to the incoming signal direction. This arbitrary datum is provided by the reference phase generator G.

In an experimental installation as illustrated in Figures 1 to 3 very satisfactory results were obtained at frequencies as high as mc./ s. the maximum errors observed being only i 2 /2%. Another advantage is that there is only one feeder to the receiver. There are no mixing circuits, insertion losses are at a minimum, and the direction finder possesses only one zenithal polar diagram thereby avoiding the errors due to varying sensitivity which occur in certain systems having noucoincident diagrams. Figure 4 shows, in manner similar to Figure 3 a preferred embodiment in which unipoles U1, U2, U3, U4 and U5 replace the dipoles 1 to 5 of Figure 3, being spaced in the same manner as are those dipoles. The unipole U5 is the central aerial, the unipoles U1 and U2 constitute one pair of aerials and the unipoles U3 and U4 the other, perpendicular pair. All the unipoles are similar vertical aerials mounted on an earth plane or screen represented by the oval line S and the aerials of each pair are, as before, approximately a quarter of a wave length apart. Simple leads marked L1 to L l-for example co-axial cablesmay be used to connect the unipoles U1 to U4 to the stator of the goniometer and a similar lead connects the unipole US to the receiver 6. With this arrangement, if the goniometer is in the position of maximum coupling with one pair of aerials the said aerials, in conjunction with the central aerial U5, act in effect as a directional Yagi system. The operation is generally as described in connection with Figure 3, like parts in the two figures being indicated by like references.

I claim:

1. A radio direction finder comprising two similar mutually perpendicular pairs of spaced aerials and a central aerial, two impedances of difierent values so chosen that when one is fully coupled as a terminating impedance to one and the other is fully coupled as a terminating impedance to the other of two aerials of a pair said one aerial acts substantially as a director and said other acts substantially as a reflector for the central aerial, a rotary coupling device having a stator with elements coupled to the four spaced aerials and a rotor with elements coupled to the two impedances and adapted, on rotation, to couple said impedances in turn to the two pairs of spaced aerials, one to each aerial of a pair, a receiver fed from the central aerial, means driven in synchronism with said rotor for producing a reference phase signal, means for comparing said reference phase signal with the phase of the output from the receiver and a direction indicator actuated by the output from the phase comparing means.

2. A direction finder according to claim 1 wherein the aerials consist of two mutually perpendicular pairs of unipoles and a central unipole, the unipoles of each pair being spaced a quarter wave length apart.

3. A direction finder according to claim 1 wherein the aerials consist of two mutually perpendicular pairs of dipoles and a central dipole,-the dipole of each pair being spaced a quarter wave length apart.

4. A direction finder according to claim 1 wherein the rotary coupling device is a capacity goniometer with a stator connected to the aerials and a rotor connected to the impedances.

5. A direction finder according to claim 1 wherein the rotary coupling device is a capacity goniometer with a stator connected to the aerials and a rotor connected to the impedances said goniometer comprising four stator plates arranged round a circle and each coupled to one of the four aerials of the two pairs, and two diametrically opposite rotor plates one earthed through one impedance and the other earthed through the other.

6. A direction finder according to claim 1 wherein the rotary coupling device is a capacity goniometer with a stator connected to the aerials and a rotor connected to the impedances said goniometer comprising four stator plates arranged round a circle and each coupled to one of the four aerials of the two pairs, and two diametrically opposite rotor plates one earthed through one impedance and the other earthed through the other the stator plates being of sinusoidal shape and the rotor plates of part cylindrical shape.

References Cited in the file of this patent FOREIGN PATENTS Number Country Date 470,596 Great Britain Aug. 18, 1937 653,406 Great Britain May 16, 1951 

